Use hydrangea cut-out from gum paste flower set to imprint design around base of cake, with points on side touching. Dust cut-out with cornstarch between imprints as needed.
Use tip 5, a disposable decorating bag with coupler and gray icing to pipe four bead petals inside imprint. Use small end of veining tool to mark center of each petal. Pipe tip 5 dot flower center. Use tip 1 to pipe dots around imprinted flower.
Insert peony in flower spike. Insert flower spike in cake top.